Accessing copper oxidation states of dissolved negative electrode current collectors in lithium ion batteries.

A novel capillary electrophoresis (CE) method with ultraviolet-visible spectroscopy (UV-Vis) detection for the investigation of dissolved Cu+ and Cu2+ in lithium ion battery (LIB) electrolytes was developed. This method is of relevance, as the current collector at the anode of LIBs may dissolve under certain operation conditions. In order to preserve the actual oxidation states of dissolved copper in the electrolytes and to prevent any precipitation during sample preparation and CE measurements, neocuproine (NC) and ethylenediamine tetraacetic (EDTA) were effectively applied as complexing agents for both ionic copper species. However, precipitation and loss of the Cu+ -NC-complex for quantification occurred in presence of the commonly applied conducting salt lithium hexafluorophosphate (LiPF6 ). Therefore, acetonitrile (ACN) was added to the sample in order to suppress this precipitation. Dissolution experiments with copper-based negative electrode current collectors in a LIB electrolyte were conducted at 60°C under non-oxidizing atmosphere. First findings regarding the copper species via CE revealed dissolved Cu+ and mainly Cu2+ . However, primarily Cu+ dissolved from the passivating oxide layer (Cu2 O and CuO) of the current collector due to the formation of acidic electrolyte decomposition products. Due to the instability of Cu+ in the electrolyte a further disproportionation reaction to Cu0 and Cu2+ occurred. The results show the high potential of this CE method for prospective investigations regarding the current collector stability in new battery electrode formulations and correlations of dissolution events with dissolution mechanisms and battery cell operation conditions.

Investigating the oxidation state of Fe from LiFePO4 -based lithium ion battery cathodes via capillary electrophoresis.

A capillary electrophoresis (CE) method with ultraviolet/visible (UV-Vis) spectroscopy for iron speciation in lithium ion battery (LIB) electrolytes was developed. The complexation of Fe2+ with 1,10-phenantroline (o-phen) and of Fe3+ with ethylenediamine tetraacetic acid (EDTA) revealed effective stabilization of both iron species during sample preparation and CE measurements. For the investigation of small electrolyte volumes from LIB cells, a sample buffer with optimal sample pH was developed to inhibit precipitation of Fe3+ during complexation of Fe2+ with o-phen. However, the presence of the conducting salt lithium hexafluorophosphate (LiPF6 ) in the electrolyte led to the precipitation of the complex [Fe(o-phen)3 ](PF6 )2 . Addition of acetonitrile (ACN) to the sample successfully re-dissolved this Fe2+ -complex to retain the quantification of both species. Further optimization of the method successfully prevented the oxidation of dissolved Fe2+ with ambient oxygen during sample preparation, by previously stabilizing the sample with HCl or by working under counterflow of argon. Following dissolution experiments with the positive electrode material LiFePO4 (LFP) in LIB electrolytes under dry room conditions at 20°C and 60°C mainly revealed iron dissolution at elevated temperatures due to the formation of acidic electrolyte decomposition products. Despite the primary oxidation state of iron in LFP of +2, both iron species were detected in the electrolytes that derive from oxidation of dissolved Fe2+ by remaining molecular oxygen in the sample vials during the dissolution experiments.

Fast sample preparation for organo(fluoro)phosphate quantification approaches in lithium ion battery electrolytes by means of gas chromatographic techniques.

Lithium ion batteries are essential power sources in portable electronics, electric vehicles and as energy storage devices for renewable energies. During harsh battery cell operation as well as at elevated temperatures, the electrolyte decomposes and inter alia organo(fluoro)phosphates are formed due to hydrolysis of the conducting salt lithium hexafluorophosphate (LiPF6). Since these phosphorus-containing decomposition products possess a potential toxicity based on structural similarities compared to chemical warfare agents, quantification is of high interest regarding safety estimates. In this study, two comprehensive approaches for the precipitation of highly concentrated PF6¯ were investigated, allowing the separation from target analytes (organo(fluoro)phosphates) and improving mass spectrometry-based quantification techniques. Trimethyl phosphate was used as a polar, non-acidic organophosphate reference substance for method development via liquid chromatography-mass spectrometry. Six solvents were examined regarding precipitation reaction and selectivity. Thermally degraded electrolytes were analyzed after precipitation by means of gas chromatography-flame ionization detector, demonstrating the applicability of the developed sample preparations. The optimized method was applied successfully without influencing any volatile and non-acidic decomposition products. Using optimized conditions, a precipitation rate of 98% PF6¯ was achieved. Consequently, a fast and easy sample preparation for gas chromatographic investigations on lithium ion battery electrolytes was implemented, applicable for routine analysis.

Mn2+ or Mn3+ ? Investigating transition metal dissolution of manganese species in lithium ion battery electrolytes by capillary electrophoresis.

A new CE method with ultraviolet-visible detection was developed in this study to investigate manganese dissolution in lithium ion battery electrolytes. The aqueous running buffer based on diphosphate showed excellent stabilization of labile Mn3+ , even under electrophoretic conditions. The method was optimized regarding the concentration of diphosphate and modifier to obtain suitable signals for quantification. Additionally, the finally obtained method was applied on carbonate-based electrolytes samples. Dissolution experiments of the cathode material LiNi0.5 Mn1.5 O4 (lithium nickel manganese oxide [LNMO]) in aqueous diphosphate buffer at defined pH were performed to investigate the effect of a transition metal-ion-scavenger on the oxidation state of dissolved manganese. Quantification of both Mn species revealed the formation of mainly Mn3+ , which can be attributed to a comproportionation reaction of dissolved and complexed Mn2+ with Mn4+ at the surface of the LNMO structure. It was also shown that the formation of Mn3+ increased with lower pH. In contrast, dissolution experiments of LNMO in carbonate-based electrolytes containing LIPF6 showed only dissolution of Mn2+ .

Preparative hydrophilic interaction liquid chromatography of acidic organofluorophosphates formed in lithium ion battery electrolytes.

The expansion of lithium ion battery (LIB) application is accompanied by the growth of battery pack sizes. This progression emphasizes the consideration of electrolyte safety as well as environmental aspects in case of abuse, accident, or recycling. Hexafluorophosphate is one of the most commonly used conducting salt anions in electrolytes. It has great potential to degrade to various acidic and non-acidic organo(fluoro)phosphates with presence of water and during battery cell operation. Consequently, toxicological investigation on these organo(fluoro)phosphates has emerged because they either have structural similarities as chemical warfare agents or play a widespread physiological role as phosphates in the human body. This circumstance underlines the need of isolated examination of these compounds for safety assessment. In this work, we used hydrophilic interaction liquid chromatography for the extraction of acidic organofluorophosphates from thermally aged LIB electrolytes. The developed two-step fractionation method provided high separation selectivity towards acidic head groups, which allowed the separation of undesired matrix and target compounds. These findings facilitate isolated toxicological investigations on organofluorophosphates that are beneficial for environmental and safety research, the battery cell industry, and human safety surveillance in regard to aged LIB electrolytes.

Surface Modification of Ni-Rich LiNi0.8Co0.1Mn0.1O2 Cathode Material by Tungsten Oxide Coating for Improved Electrochemical Performance in Lithium-Ion Batteries.

Ni-rich NCM-based positive electrode materials exhibit appealing properties in terms of high energy density and low cost. However, these materials suffer from different degradation effects, especially at their particle surface. Therefore, in this work, tungsten oxide is evaluated as a protective inorganic coating layer on LiNi0.8Co0.1Mn0.1O2 (NCM-811) positive electrode materials for lithium-ion battery (LIB) cells and investigated regarding rate capability and cycling stability under different operation conditions. Using electrochemical impedance spectroscopy, the interfacial resistance of uncoated and coated NCM-811 electrodes is explored to study the impact of the coating on lithium-ion diffusion. All electrochemical investigations are carried out in LIB full cells with graphite as a negative electrode to ensure better comparability with commercial cells. The coated electrodes show an excellent capacity retention for the long-term charge/discharge cycling of NCM-811-based LIB full cells, i.e., 80% state-of-health after more than 800 cycles. Furthermore, the positive influence of the tungsten oxide coating on the thermal and structural stability is demonstrated using postmortem analysis of aged electrodes. Compared to the uncoated electrodes, the surface-modified electrodes show less degradation effects, such as particle cracking on the electrode surface and improvement of the thermal stability of NCM-811 in the presence of electrolyte.

Deciphering the lithium ion movement in lithium ion batteries: determination of the isotopic abundances of 6Li and 7Li.

Lithium ion batteries (LIBs) are the energy storage technology of choice in the context of renewable energies and electro-mobility. It is imperative to get a thorough understanding of the aging mechanisms to achieve a prolonged cycle and calendar life. One major drawback of the technology is continuous capacity fading during operation, which is partly attributed to the loss of active lithium, the object of this work's analysis. While lithium ion battery aging is an intensively researched topic, there is still the need to determine the origin of the lost lithium and the lithium migration into the different cell components over time. To achieve this goal, different plasma-based mass spectrometric techniques in combination with isotope analysis are applied to obtain bulk as well as depth-resolved information about lithium ion movement and distribution of lithium in aged LIB cells. Different aging experiments are performed on NCM622/graphite cells with a 6Li-enriched electrolyte with subsequent Li analysis of the cell components. The results show that the charging rate, as well as the cycle number, has an impact on the 6Li/7Li-abundances and that the overall abundances show a rapid mixing of the isotopic species already after the first charge/discharge cycle for all cell components.

Adaptation and improvement of an elemental mapping method for lithium ion battery electrodes and separators by means of laser ablation-inductively coupled plasma-mass spectrometry.

In this study, laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was applied to previously aged carbonaceous anodes from lithium ion batteries (LIBs). The electrodes were treated by cyclic aging in a lithium ion cell set-up with LiNi0.5Mn1,5O4 (LNMO) cathodes and hard carbon (HC)/mesocarbon microbead (MCMB) anodes. An inhomogeneous transition metal deposition pattern could be induced by replacing the spacer in a standard coin cell set-up with a washer. The inhomogeneity pattern matched the dimension of the washer depicted by the hole in the center. These transition metal (TM) patterns were used to optimize higher lateral scanning speeds and frequencies on the spatial resolution of the mapping experiments using LA-ICP-MS. Higher scanning speeds had an observable influence on the resolution of the obtained image and an overall saving of 60% with regard to time and gas consumption could be achieved. Additionally, the optimized method was applied to the cathode and separator in order to visualize the distribution and deposition pattern, respectively.

Individualização dos cuidados em saúde e apassivação do usuário no âmbito da educação em saúde na Estratégia Saúde da Família / Individualization of health care and making users passive in health education in the Family Health Strategy / Individualización de los cuidados en salud y pasividad del usuario en el ámbito de la educación en salud en la Estrategia Salud de la Familia

Resumo A pesquisa que originou este artigo teve como objetivo compreender as representações de profissionais e usuários da Estratégia Saúde da Família sobre educação em saúde. Tratou-se de estudo com abordagem qualitativa e técnicas de observação participante e entrevista, por meio da análise de conteúdo, realizado em 2008 e 2009. A representação do grupo denotou ‘educação’ e 'saúde' como bens de valor social, cultural e histórico a serem preservados na família e na sociedade em geral, ancorando o cuidado com a saúde em estratégias que se sobrepõem à prescrição de procedimentos e comportamentos. No entanto, profissionais e usuários dos serviços de saúde associam ‘educação em saúde’ à transmissão de conhecimentos técnicos específicos, a ser realizada por profissionais capacitados. Nas práticas de educação em saúde, prevalecem: prescrição de hábitos saudáveis na dimensão individual; grupos temáticos focados em enfermidades ou estados de saúde específicos; comportamento passivo dos usuários; e dificuldades de adesão e ações de caráter compulsório. A transmissão de conhecimento e a prescrição de hábitos para o autocuidado individual são as formas prevalentes de representar a educação em saúde para todos os sujeitos da pesquisa. As práticas de educação em saúde observadas podem ser caracterizadas como práticas tradicionais de atenção à saúde.

Abstract The study that originated this article aimed to understand the representations of Family Health Strategy professionals and users about education in health. It was an study carried out using a qualitative approach and participant observation and interview techniques through content analysis. It was conducted in 2008 and 2009. The group's representation denoted ‘education’ and ‘health’ as assets of social, cultural, and historical value that should be preserved in the family and in society at large, anchoring health care on strategies that overlap the prescription of procedures and behaviors. However, health service professionals and users associate ‘health education’ to the conveyance of technical knowledge, which should be done by trained professionals. Prevailing in health education practices were prescribing healthy habits in the individual dimension; thematic groups focused on specific diseases or health conditions; the users' passive behavior; difficulties in adherence, and mandatory actions. All study subjects viewed the conveyance of knowledge and the prescribing of habits for individual self-care the prevalent ways of representing health education. Observed health education practices can be characterized as traditional health care practices.

Resumen La investigación que originó este artículo tuvo como objetivo comprender las representaciones de profesionales y usuarios de la Estrategia Salud de la Familia sobre educación en salud. Se trató de un estudio con enfoque cualitativo y técnicas de observación participante y entrevista, por medio del análisis de contenido, realizado en 2008 y 2009. La representación del grupo denotó “educación” y “salud” como bienes de valor social, cultural e histórico a ser preservados en la familia y en la sociedad en general, anclando el cuidado con la salud en estrategias que se sobreponen a la prescripción de procedimientos y comportamientos. Sin embargo, profesionales y usuarios de los servicios de salud asocian “educación en salud” a la transmisión de conocimientos técnicos específicos, a ser realizada por profesionales capacitados. En las prácticas de educación en salud, prevalecen: prescripción de hábitos saludables en la dimensión individual; grupos temáticos centrados en enfermedades o estados de salud específicos; comportamiento pasivo de los usuarios; y dificultades de adhesión y acciones de carácter compulsorio. La transmisión de conocimiento y la prescripción de hábitos para el autocuidado individual son las formas prevalentes de representar la educación en salud para todos los participantes de la investigación. Las prácticas de educación en salud observadas pueden caracterizarse como prácticas tradicionales de atención de la salud.

Magnetism and variable temperature and pressure crystal structures of a linear oligonuclear cobalt bis-semiquinonate.

The crystal structure of the first oligomeric cobalt dioxolene complex, Co3(3,5-DBSQ)2((t)BuCOO)4(NEt3)2, 1, where DBSQ is 3,5-di-tert-butyl-semiquinonate, has been studied at various temperatures between 20 and 200 K. Despite cobalt-dioxolene complexes being generally known for their extensive ability to exhibit valence tautomerism (VT), we show here that the molecular geometry of compound 1 is essentially unchanged over the full temperature range, indicating the complete absence of electron transfer between ligand and metal. Magnetic susceptibility measurements clearly support the lack of VT between 8 and 300 K. The crystal structure is also determined at elevated pressures in the range from 0 to 2.5 GPa. The response of the crystal structure is surprisingly dependent on the dynamics of pressurisation: following rapid pressurization to 2 GPa, a structural phase transition occurs; yet, this is absent when the pressure is increased incrementally to 2.6 GPa. In the new high pressure phase, Z' is 2 and one of the two molecules displays changes in the coordination of one bridging carboxylate from µ2:κO:κO' to µ2:κ(2)O,O':κO', while the other molecule remains unchanged. Despite the significant changes to the molecular connectivity, analysis of the crystal structures shows that the phase transition leaves the spin and oxidation states of the molecules unaltered. Intermolecular interactions in the high pressure crystal structures have been analysed using Hirshfeld surfaces but they cannot explain the origin of the phase transition. The lack of VT in this first oligomeric Co-dioxolene complex is speculated to be due to the coordination geometry of the terminal Co-atoms, which are trigonal bipyramidally coordinated, different from the more common octahedral coordination. The energy that is gained by a hs-to-ls change in Oh is equal to Δ, while in the case of the trigonal bipyramidal (C3v), the energy gain is equal to the splitting between d(z(2)) and degenerate d(x(2) - y(2))/d(xy), which is significantly less.